652 research outputs found

    Automatic Extraction of Commonsense LocatedNear Knowledge

    Full text link
    LocatedNear relation is a kind of commonsense knowledge describing two physical objects that are typically found near each other in real life. In this paper, we study how to automatically extract such relationship through a sentence-level relation classifier and aggregating the scores of entity pairs from a large corpus. Also, we release two benchmark datasets for evaluation and future research.Comment: Accepted by ACL 2018. A preliminary version is presented on AKBC@NIPS'1

    Sulfur isotopic compositions of submicrometer SiC grains from the Murchison meteorite

    Get PDF
    We report C, Si, N, S, Mg-Al, and Ca-Ti isotopic compositions of presolar silicon carbide (SiC) grains from the SiC-rich KJE size fraction (0.5-0.8 μm) of the Murchison meteorite. One thousand one hundred thirteen SiC grains were identified based on their C and Si isotopic ratios. Mainstream, AB, C, X, Y, and Z subtypes of SiC, and X-type silicon nitride (Si₃N₄) account for 81.4%, 5.7%, 0.1%, 1.5%, 5.8%, 4.9%, and 0.4%, respectively. Twenty-five grains with unusual Si isotopic ratios, including one C grain, 16 X grains, 1 Y grain, 5 Z grains, and 2 X-type Si₃N₄ grains were selected for N, S, Mg-Al, and Ca-Ti isotopic analysis. The C grain is highly enriched in ²⁹Si and ³⁰Si (δ²⁹Si = 1345‰ ± 19‰, δ³⁰Si = 1272‰ ± 19‰). It has a huge ³²S excess, larger than any seen before, and larger than that predicted for the Si/S supernova (SN) zone, providing evidence against the elemental fractionation model by Hoppe et al. Two SN models investigated here present a more satisfying explanation in terms of a radiogenic origin of ³²S from the decay of short-lived ³²Si (τ1/2 = 153 yr). Silicon-32 as well as ²⁹Si and ³⁰Si can be produced in SNe by short neutron bursts; evidence for initial 44Ti (τ1/2 = 60 yr) in the C grain is additional evidence for an SN origin. The X grains have marginal ³²S excesses, much smaller than expected from their large ²⁸Si excesses. Similarly, the Y and Z grains do not show the S-isotopic anomalies expected from their large Si isotopic anomalies. Low intrinsic S contents and contamination with isotopically normal S are the most likely explanations
    corecore